Telephone system



Jan. 15, 1929.

n l A B D WILLIS TELEPHONE SYSTEI riledreb. 24, 192e ummm I Bernard D. hhlhs CVI CLI

Patented Jan. 15, 1929.

UNITED- STATES 1,698,979 PATENTv GFFICE.

BERNARD D. WILLIS, OE OAK PARK, ILLINOIS, ASsIGNoR, BY MESNE ASSIGNMENTS,

To AUTOMATIC ELECTRIC INC., WARE.

OE VCI-IICaG-o, ILLINOIS, A CORPORATION OE DELA- TELEPHONE SYSTEM.

Application led February 24, 1926. Serial No. 90,241.

This invention relates Vto telephone systems in general, but more speciiically to toll or long distance trunkine' systems in which the toll connections within a certain area are established and Supervised from a main toll board.

In larger telephone Systems comprising several exchanges, or extending over an area including several Surrounding communities, the practice of completing and supervising all toll connections within that area from a main toll board centrally located with respect to the other exchanges or communities is sometimes found desirable. All the toll lines incoming from distant points into a telephone system following this practice terminate at the main toll board trom where toll service lines extend to the various exchanges in the local system. For well known engineering reasons, the trunk lines between exchanges, especially within the limits ot' a city, are usually run in cables, while the trunk lines between cities are usually opennvire lines. It is therefore common practice to terminate the incoming open-wire lines at some outlying exchange from where they are extended by cable to the main gtoll board.

Should a toll connection be desired with a subscriber served by the outlying exchange through which the incoming toll trunks pass, thcrtoll connection would ordinarily extend troni the distant point over a toll trunk through this outlying exchange to the main toll board at which the connection would be completed by the toll operator over a local service toll line back again to the outlying exchange to the local subscriber. Ina-smuch as the transmission losses in toll connections is an important consideration, especially wnen the trunk lines are run in cables, the transmission losses in cables beingV comparatively igh, it becomes desirable to reduce the length of the talking circuit ot a toll connection as much as possiblej and especially desirable to eliminate the.

looping back ot a connection, as would ordinarily be necessary to complete a connection such described above. By thisinvent-ion, means have been provided whereby such a toll connection may be completed and supervised from the main toll board at the same time making it possible to establish a talking connect-ion over the mest direct rout-e to the called subscriber, eliminating the sections of trunk lines from the outlying exchange to the toll board and back `again from the talking circuit.

A section of a telephone system employing the scheme proposed by this invention is diagrammatically shown in the accompanying drawing comprising Fig. 1 and Fig. 2. In Fig. 1, the various switches and circuits pertaining to the invention are represented diagrammatically and are shown more `in detailvby means of the usual schematic circuit diagrams Iin Fig. 2. The corresponding element-s are lettered and numbered the same in both figures. v

Referring to F ig. 1 of the drawings, the trunk line comprising conductors 101 and 102 is one vof the incoming toll lines from some distant city. The toll lines terminate at the exchange Y from where they extend to the main toll board located in exchange X, terminating in jacks, such as J. The conductors 103 and 104 comprise that section ot an incoming trunk line extending from the exchange Y to the toll board. The exchange `Y in this instance, is an automatic exchange. The conductors 305.21m! 306 comprise one of the toll service lines extending from the main toll board to the exchange Y, accessible at the toll board in jacks such as jack J. Each toll service line terminates at the automatic exchange Y in a toll transmission selector. The toll transmission selectors have access totoll connectors which in turnhave access to the subscribers linev served. by the automatic exchange Y.

At the automatic exchange Y special connecting links, such C-C, to which this invention particularly pertains, have access on one end to the incoming toll trunks passing through this exchange fromthe distant point to the toll board, and on the other end to the toll service lines extending from the toll board to the automatic exchange Y. A special line comprising conductors 201 and 202 extends from the main toll board to the automatic exchange Y, terminating there in the line switch LS. Y At ,the main toll board` the dial S .may be bridged across this line by means of a key.A The line switch LS has access in its banks to all the connecting links, such as C-C. The toll operator at the main toll .board is provided with cords, such ascord O. Y ,K A y A brief description of the above mentioned los f 101 and'102 is the trunk selected.

apparatus will now be given, particular reterence being made to Fig. 2.

The connecting link C-C consists essentially of two separate vertical and rotary switching mechanisms of the Well known Strowger step-by-step type Whose wipers may be inductively connected together. The control circuits for these switching mechanisms are interconnected and are so arranged that a common line relay first controls the opera-tion of the switching mechanism C, which has access to the toll service lines, and then controls the operation of the switching mechanism C, which has access to the yincoming` toll trunks.

The line switch LS is an ordinary rotary line switch having Wipers which rotate in one direction only and which have no normal position.

The cord O is provided With the dial S, the telephone set TS, and the supervisory lamps L and L. The generator G is common to all the cords at the operators position. n

A toll transmission selector' and a connector are not shown, since they do not pertain particularly to the invention, and are merely represented by rectangles labelled EF and H, respectively. Reference may be made, however, to the licks Patent No. 1,633,149, granted June 2l, 1927, in Which is shown a suitable toll transmission selector and toll connector.

A clear understanding of the invention and its objects, and also other features not specially mentioned, may be obtained from a detailed description of the operation of the various switches and circuits pertaining to the invention. For this purpose, it Will be assumed that a long distance connection is desired by a party in some distant city With the subscriber at the substation A, Whose line terminates in the automatic exchange Y. To establish this connection, the toll operator in the distant city selects a toll trunk extending to the exchange Y and applies ringing current thereto. It may be assumed that the trunk line comprising conductors The ringin?,` current incoming over conductors 101 and 102, which extend by Way of armatures 80 and 87 ane their resting;l contacts, conductors 103 and 104, closed springs 7 and 8, to

the drop signal 2, operates this signal which notu'ies the toll operater at the main toll boa-rd ol' the incoming toll call. Iuresponse to Y this signal, the toll operator inserts the plug ol' an idle cord, such as plug P et' the cord O, into the jack J and operates the listening key K. The distant toll operator then informs the local toll operator at the main toll ioard of the connection desired. Since it has been assumed that the toll call is for the subscriber at substation A in the exchange Y, the toll operator inserts the plug P into the Lesaeve jack of an idle toll service line extending back to the automatic exchange -Y. t may be assumed that the trunk selected is the one comprising` conductors 305 and 306, terminating in the jack J. After insertingthe plug P into the jack J, the operator throws the key K2 toA the dialling position, thereby bridging the dial S directly across the conductors 305 and 306 by the closure of contacts and l0 and the opening of contacts 15 and 16. The operator then dials the directory number et the subscriber substation A. ln response to the bridging ot the dial across the line conductors and the dialling of the digits by the operator, the toll transmission selector EF and the toll connector H unct-in to establish a connection to the desired substation in the Well known manner. The detailed operation ot the ,toll transmission selector and the toll connector are described in the above mentioned `Wicks patent, to which reterence may be made.

t may be 'assumed that the line to substation A is idle at the time the connector' is operated Which will be indicated by 'the lighting of the lamp L after the operator has completed the dialling, as is described in the above mentioned application. iinishing dialling and perceiving the illumination ot the lamp L', the operator` at the main toll board may signal the subscriber at substation A at will by operating the key K2 to the ringing-position. Ringing current applied to the conductors 305 G starts the usual signalling` operation which causes the ringing of the bell,4 at the subscribers substation A.

WYhile the called subscriber is being the operator may proceed to prepare a e necting link at the automatic exchange, `such as connecting link C-C for establishing a talking` connection from the toll trunk to conductors 305 and 300 at the automV exchange directly, the purpose being toeliminate the loop extending from the automatic exchange to the toll board and then back again to the automatic exchange from the talking circuit. Each toll trunk passing through the automatic exchange and terminating at the toll board, and also each toll service line extending -from the toll board back to the automatic exchange is assigned a certain number. The toll service lines are accessible in the banks of the switching mechanisms, such as C, and the incoming toll trunks are accessible in the banks of the switching mechanisms, such as C, a particular line or trunk being accessible in 'the set or' bank contacts corresponding to the number of that line or trunk. To accomplish the purpose described above, the operator operates the dial key KS and then dials the numbers and 34, consecutively, it being assumed that these are the numbers or" the toll service' lines and the incomingtrunk lines used,` respectively. Operating the dial key K3 bridges thev dial S across the con-v ductors 201 and 202, thereby closing a circuit for the line relay 2l ot the line switch LS. Relay 2l operates and places ground on the upper terminal of switching relay 22 and also connects the test wiper to the junction ot' the lower winding of the switching rela-y 22 and the stepping magnet 23 at aL mature 24. If the conductors terminating at the contacts upon which the switch wipers 3l-33, inclusive, are positioned at this time extend to a busy connecting link, ground will be present on the bank contact engaged by the wiper 32. This will cause the operation of the stepping magnet in the well known manner over a circuit which may be traced from ground on the bank contact engaged by wiper armature 27 and the resting Contact, working contact Vand armature 24, interrupter springs 29, through the winding ot the stepping magnet to battery` tepping magnet operates, opens the interrupter springs 29, thereby opening its own circuit, and in deenergizing, steps the wipers 231-33, inclusive, into engagement with the next set of bank contacts. Ti' the conductors terminating in this next set of bank contacts also extend to a busy connecting link, the stepping magnet 23 will again function to step the wipers into engagemcnt with the next set of bank contacts. This operation will be repeated until the wipers 31-33, inclusive, are rotated into engagement with the set of bank contacts terminating conductors connected to an idle connecting link, an idle connecting link being represented by the absence of ground on the test contact engaged by the wiper 32. Then, due to the absence of ground on the test Contact, no circuit is again closed for the stepping magnet 23, Vand the short circuit is also removed from the switching relay 22. The switch wipers are arrested in this position and switching relay 22 is energized over a circuit from ground at the working cont-act and armature 25, through the winding of the switching relay 22, closed interrupter contacts 29', through the finding ot the stepping relay to battery. The resistance et the winding of relay 22 does not permit suiiicient current to tlow to cause the operation of stepping magnet at this time. Relay 22 operates, however, and disconnects conductors 201 and 262 from their normal battery and ground connections, and connects them to the switch wipers 31 and 33 at armatures and 2S and their working contacts, respectivelyg and also places ground potential on the bank contact engaged by wiper 32 at armature 27 and the working Contact. In the description of the operation of the line switch LS, it has. been assumed that the wipers 31433, inclusive,

may not be positioned on contacts connected to an idle connecting link at the time the key KS is operated. It will become obvious fronrlater description, however, that the wipers of the line switch LS by reason ot' other considerations to be explained later will most probably be standing opposite an idle trunk, providing there is one idle when the key K3 is thrown.

It may assumed that the wipers S31-33, inclusive, are in, or were rotated into, engagcment with the bank contacts i4-36, inclusive, terminating the connecting link C-C, which may be assumed to be idle at this time. The connecting ot the conductors 201 and 202 to the wipers 3l and respectively, closes a circuit for the' line relay 43. Line relay 43 operates and closes a circuit YFor the release relay 44 at armature and the working contact. Release relay 44 operates and prepares the impulse circuit for the vertical magnet 48 at armature 5G. and also places ground on the holding conductor 37 at :.u'mature 55, this occurring bcfore the slow acting' line relay 2l in the line switch LS has had time to restore its armature following the 'opening of its circuit which occurs when switching relay 22 ener- The switching relay 22 is now held operated from ground supplied to the release conductor 37.

Thev foregoing operations of the line switch LS and the operations of relays 43 and 44 all take place responsive to the operation of the key K3. In response tothe dialling of the digit 5, the line relay 43 deenergizes and energizes again a corresponding number of times. The first time the armature 54 falls back, a ground impulse is sent to the Vertical magnet 48 by way of armature 53 and its resting contact, armature 5i and its resting contact, Aarn'iaturc 54 and its resting contact, armature 56 and its working contact, closed springs 64, through the winding of the series relay 45, through the winding of the vertical magnet 48 to battery. Vertical magnet 48 operates and eleyates the switch wipers 81-84, inclusive, one step. This operation shifts the vertical ott normal springs, opening springs 64 and closing springs 63. Series relay 45 also energizes and operates its armature 57. The remaining impulses of the first digit traverse the same path as the initial impulse, cxcept that the path now includes springs 63 and armature 57 and its working Contact, and excludes springsl 64, series relay 45 being slow acting. maintaining its armature attracted throughout the vertical movement. lipers 81-84, inclusive, are thus raised opposite the fifth level of bank contacts. At the termination ofY the first series of impulses, relay 45 falls back and prepares a circuit for the rotary magnet 49 at armature 57 and its resting Contact.

lees

Gl armature 59 and its resting' coe t a n V through the Winding of the r. iarv serie relay 47, through the Winding et 'the rot magnet 49 to battery. Rotary series relay operates and at armature 6l changes tl circuit for the rotary magnet 49 to the Working contact and armature exclues armature 59 and its res .ing cont Relay 47 also closes a circuit for the lower 'Winding of the two-step relay 45 armature 60 and the working contact. The twostep relay 46 partially energizes and operates its armature 53, thereby preparing` a circuit tor fully opelating, which it is y Vented from doing at this time since ground is connected to both ends of its upper Wi l ine'. From the foregoing description, might appear that the conductor 512 cor be connected directly to the armature 59, thus dispensing with armature 6l and l" contacts controlled thereby, since armature 59 does not operate until the completion of the rotary movement. Ari ature 6l and the contacts controlled thereby are providl nevertheless, to assure the proper opera) 7 non of the rotary magnet 49 even though the, tivo-step relay 46 is not properly adpisted and permits the separation of armature 59 and its resting Contact when only partially energized To continue, the rotary magnet 49 operates and rotates the switch rifipers 3l -34, inclusive, into engagement with the sixth set of contacts in the fifth level, this set comprising the contacts ll-'94 inclusive, at which the toll service "',ne comprising conductors 305 and 306 is accessible. At the end of the rotary movement, rotary series relay 47 deenergiaes and removes the short circuit from the upper Winding oiE the two-step relay 4G. Two-stop relay 4G is new energized over two windings in series from ground by way of armature 55 and the Working Contact, armature 53 and the Working contact, through the upper a lower windingsr oi' the two-step relay 45 tf. battery. The resulting increased magnetic pull causes the operat on ot armature thereby preparing a circuit tor the vertical magnet 4S o'l2 the switching` mechanism.

rlhe operator now dials the digit 3, and, in response to the impulses produced thereby, ground impulses are again sent over a circuit Which is the same as that previously traced to arma-ture 59 trom Where it extends actuating; Key

by Way oli the Working contact olE armature 59, normally closed off normal springs 46, through the Winding oi" the Vertical se liesI relay through the Winding ot' the vvertical infifi'net 48 to battery. Vertical magnet 43 ope ates, just as did vertical. magnet 48, and raises the Wipers 81483, inclusive. opposite the third level of banlz contacts, shitting the oil normal springs 63 and 64, on the that step or the Wipers, the impulsing path lf'or the remaining impiiilses to include 'the springsV 63' and armature 57 and the Working Contact and to exclude springs 64, so that when relay 45 falls baci; the operating` circuit will be shift l to rotary magnet 49.

rllhe toll operator will not dial the las dioit immediately, since the .dialling of th Will become evident from later last i t, as

se il initiates Jihe operation of connecting the toll trunk conductors 101 an'l 102 directly to the conductors 30G and 30.5",

and tor have supervision directly throirgh her position until the calling and called parties are actually in talk' V; communication. She will, therefore, Wait until this has oeen veri lied betere dialling the last digt. ln the meantime, lshe may disconnect her telephone set Jtrom the c -rl al d ansvrer other calls.

Should the distant toll operator Wish to signal the toll operator at any time before c connection has linally been completed, che can do so by again applying ringing current to the toll. conductors 1014-102 still connected to the toll conductors 103 and 104. lhe supervisory relay 3, bridged across the talking conductors or the cord, will then operate and will close a locking circuit for itsel; and for the supervisory lamp L at This relay will remain operi A 'the lamp 1will remain lighted until ,e main toll operator again connects her l across the toll line in question ting the listening hey l to conivith' the distant toll operator. Operfing the lei l. ridges the telephone cross the talking conductors ot the cord nd causes the separation or the springs G opens the locking circuit for the supervisory relay 3 and also opens the circuit for the lamp ll.

When the .subscriber at the substation removes his receiver. the lamp L is eatinhed, thereby notifying the toll operator Y he called subscri" er has answered. She may nonv signal the litant toll operator by actuating the lrey l to the 'signalling position, thereby connecting the generator o the toll trunk conductors 103 and 194 springs 1? and 1'", respectively, and l connect her telephone set to the cord (l by c When the distant toll thereby changing operated to prepare this linlr for operation.

lllhen the toll operator restores the loy K3, however, the bridge across the conductors 201 and 202, is opened, hus opening tlc circuit of this second operated line relay. rlhis relay will dcenergize and open the circuit of the second operated release relay. lt may be mentioned, hovvever, that it is not necessary 'for the main tolloperator to restore the key K3, should she malte successiveconnectionsot the type just descr-i, ed,

tically opsince the line switch LS autom. i erates topcsition its wipers on a set ot contacts connected to an idle connecting link immediately tollowing` the completion ot the dialling ot the tour dig'ts -for setting up a connection.

lJVhen the subscriber at the substation A replaces his receiver at the end ot the conversation, lamp L is again lighted. ln response to the lighting ot the lamp L', indieating the termination ot the conversation, the toll operator removes the plug la from the jack J. The removal ot the plug l Vtrom the. jack J causes the release ot the toll connector and the toll transmission selector' in the well known manner. Ground potential is then removed trom the rele se ductor 98, thereby opening the circuit for the holding relay 4t2. Relay 42 deenergizes and removes the ground supplied to the holding conductor 37 at the working Contact ot armature 52. Ground is maintained on conductor 37, however, until armature 5l is released by way of this armature and its working contact, and resting contact and armature 52. At armature 53, the circuit of relay il is opened as soon as relay Ll), deenergizes, and a point in the release circuit vis closed. Relay ell releases a short time a'lter its circuit is opened and removes ground from conductor 37 at armature 5l, thereby openingthe circuit ot relay i6 the switching relay 7l and the switching-control relay-46. ln releasing, relay il also closes the circuit for the release magnets 50 and 5l, which may be traced from ground at armature 53 and its` resting contact, arniatmfe 5l and its resting contact, armature vand its resting contact, armature 56 and its resting contact, through the oil normal springs G2, closed upon the iirst vertical step ot the wipers of the switching mechanism C through the winding oit the release magnet 50 to battery and also through the oil normal springs 62 closed upon the first vertical step of the switching mechanism C, through the winding of the release. magnet 50 to battery. Relays 4:6, 46 and 7l deenergize and restore their armatures to normal. As a result ot the restoration ot relay 7l, the

' circuits oit the relays 12 and 85 are opened,

causing their deenergization. Release magnets 50 and 50 energize, release magnet 50 operating to release the wipers ot the switchringing position, thereby extending current from .the generator' by or springs l? and 17', tip and ri g ot p g l), tip and ring ot gael; J, conductors 101i and 103, resting contact and armatures 87 and 86, over trunk conductors 102 and lOl to the distant toll operators position. il Yter `giving the toll operator the disconnect signal, the toll operator at the main toll board removes the plug P from the jack J. Thus all apjaratus is again restored to normal.

From the foregoing descriptions, it is evident that simple and eflicient method has been devised whereby an incoming toll call over a toll trunk passing through the exchange which serves the subscriber with which connection is desired, may be set up by the main toll operator at the main toll board in the regular manner through lier position by means ot an ordinary toil cord; whereby the toll operator, sett' up the connection in the regular way, may cause the talking connection to be extended directly ,to the subscriber througl automatic switches in the exchange serving the called subscriber and in which the cistant toll -runlr terminates, and whereby the toll opera-tor may have supervision ot this toll connection over the toll service line originally used to complete the toll connection.Y

The invention, its features and the operation of the various mechanisms involved having been described, what is con new and is desire-d to have protected l 1 ters latent will be specitically stated in the iollow ing appended claims.

lifhat claimed is:

l. .Tin a trunling system, a and a second line, cach line terminating in a iack, a cord circuit tor interconnecting s li i through the medium of their associate( jacks, a linl circuit having a set oi' movable terminals at each end, iixed terminals 'for said first line normally disconnected there trom, fixed terminals permanently connected to the conductors ot said second line, an automatic switch 'for advancing one ot said movable terminals into engagementwith the fixed terminals ot saiflsecond line, a second automatic switch tor advancin;I the other set of said movable terminals into engagement with the fixed terminals ot' the said iirst line, means tor controlling automatic switches, means tor connecting ico liO

lili

said normally disconnected fixed terminals to the conductors ot said tirs-t line, and means controlled over said second lineY for maintaining,f said switches operated independent orp said controllingl means.

2. In a telephone system', a iii-st and second line, a cord circuit, means tor connecting said lines through said cord circuit, a link circuit having' terminals at each end, an automatic switching mechanism, means for operating said mechanism to connect one end of said link circuit to said second line and the other end of said link circuit to said rst line, audmeans for maintaining sad mechanism operated over said second line independent ot said opcrat'`A means.

3. In a telephone system, an operator-s position, an operator-s cord, automA` iic exchange, a first trunk line at d exclring, f a. second trunk line extending rom Said exchange to said operators position, a third trunk line extending' from said operator-s position to said exchange, an automat' switch at said exchange, a called subscriber line, operator controlled means for establishin?,` a connection from said first trunk line to said called subscriber ria said second trunk line, said cord circuit, said third trunt; line, and said automatic switch, a. link circuit at said exchange, and operator controlled means for connecting' said first trun r line to said automatic switch directly via said link circuit independent of said sec nd trunk line, said cord circuit, and said tliird trunk line.

4. In a telephone system, an operators position, an operators cord, an automatic exchange, a iirst trunk line at "aid exchange, a second trunk line extending trom said ex change to said operators position, a third trunk line extending,` from said operatcs position to said exchange, an automatic switch. at said exchange, a called sul ,cribers line, operator controlled means .tor establishing a` connection from said first trunk line. to said called subscriber "ia said second trunk line, said cord circuit, said third trurl-z line, and said automatic switch, a link circuit at said exchange, and operator controlled means 'for connecting; said iirst trunk line to said automatic switch directly via said link circuit independent ot said secon-fl trunk line, said cord circuit, ano said third trunk line, said operator controlled means being; thereafter controlled solely over said third trunk line.

5. In a telephone system, an cperators position, an operators cord, an automatic exchange, a firsttrunk line at said exchange, a seconc trunk line extending from said exchanse, to said operators position, a third trunk line extending from said operatonc position to said exchange, an automatic switch at said exchange, a called subscribei"s line, operator controlled means for establishreconnection from said first trunk line to said called subscriber via second trunk line, saidcord circuit, said third trunk line, and said automatic switch, a link circuit at said exchange, and operator controlled means for connecting said first trunk line to said automatic switch directly via said link circuit independent otl said second trunk line, said cord circuit, and said third trunk lino, and means in said cord circuit for maintaining` supervision of said connection over said third trunk line.

(5. In a telephone system, an operators position, an operators cord, an automatic exchange, a lirst trunk line at said exchange, a second trunk line extendingy Yfrom said exchance, to said operator-'ls position, a third trunk line extending from said operators position to said exchange, au automatic switch atsaid exchange, a called subscribers line, operator controlled means for establishing a connection from said first trunk line to said called subscriber via said second trunk line, said cord circuit, said third trunk line, and said automatic switch, a link circuit atl said exchange, and operator controliedniea-ns for connecting said first trunk line to said automatic switch directly Via said link circuit independent of said second trunk line, said cord circuit, and said third trunk line, means in said cord circuit for maintaining supervision of said connection over said third trunk line, and neans` associated with said third trunk line for preventing the shunting of voice currents over said third trunk line.

7. In a telephone system, an operators position, a group of trunks terminating at said position, a second group of trunks accessible at said position, each trunk ot' said second group terminating in an automatic switch, a called subscribers line, a cord circuit, means for establishing a connection over any trunk of said first group through said cord circuit over any trunk ot' said second group and the terminatingl switch to said subscriber, a plurality ot connecting' links, an automatic switching mechanism tor each of said links, a selectingr switch having access to all of said links always connected to an idle one ot said switching mechanisms, providing there is one idle, operator controlled means for operating the switching mechanism connected to said selecting switch to connect any one of said first group of trunks to any one of saidv terminating lin a. selecting switch, a plurality ot' automatic switches accessible to sait selecting switch, said selecting switch always being in connection with an idle one et said automatic switches, providing there is one idle, second trunk line, means controlled over said tirst trunk line for operating the connected automatic switch to connect with said second trunk line, and means in said automatic switch automatically responsive to the connection ot said automatic switch with said second trunk line tor causing said selecting switch to connect with aA second idle automatic switch.

9. ln a telephone system, a temporarily established connection including a line switch and a second switch, a release 'trunk conductor, means associated with the second switch for placing a potential on said conductor to maintain said line switch operated, means associated with said second switch tor momentarily removing said potential to cause the line switch to release, and means for maintaining the second switch operated.

l0. ln a telephone system, a temporarily established connection including a line switch and a second switch, a release trunk conductor, means associated with the second switch for placing a potential on said conductor to maintain said line s vitch operated, means associated with said second switch 'tor removing said potential to cause said line switch to release, means it'or maintaining said second switch operated, and means tor re-applying said potential to guard said second switch against re-seizure by said line switch when said line switch is re-operatcd.

ll. ln a telephone system, a temporarilyv established connection including a line switch and a second switch, a release trunk conductor, means associated with the second switch tor placing a potential on said conductor to maintain said line switch operated, means associated with said second switch for removing said potential to cause said line switch to release temporarily, although its control circuit is still closed, means tor maintaining said second switch operated, and means in said second switcl tor re-applying a potential to said conductor heiore the said line switch has had time to re-operate, so that when the re-operation takes place the line switch will hunt for and seize a different switch.

l2. ln a telephone system, a pluralitT oit automatic switches7 a line switch having access thereto, means tor operating said line switch to select and connect with an idle one ot said automatic switches, means tor operating said automatic switch, means tor maintaining said automatic switch operated, and mea-ns automatically responsive to the completion of the operation of said automatic switch for causing said line switch to select a second idle automatic switch loetore said tirst automatic. switch is released.

13. ln a telephone system, a' tirst trunk line, asecond trunk line, a oord circuit, a third trunk line, a fourth trunk line, means tor extending a connection over said trunk nes and said cord circuit in series, means tor lay-passing said cord circuit and said second and said third trunk lines and 'for disconnecting` said second trunk line, and means tor maintaining supervision otl said conneftion over said third trunk line.

la. ln a telephone system, a first trunk line, a second trunk line, a third trunk line, a `fourth trunk line, means tor extending a ienne/tion over said trunk lines in s r f means-tor lay-passing said second and said third trunk lines and tor disconnecting' said second trunk line, means tor maintaii supervision et said connection over said thi d trunk line, and meansv associated with said third trunk line Yfor preventing voice current trom .being shunted over said third.

trunk line. l

l5. ln a telephone system, a first trunk, a second trunk, a third trunk, a fourth trunk, means for extending a connection over said trunks in series, means tor lip-passing said second and said third trunks by dis onneting said first trunk troni said sccor trunk and connecting it to said fourth t- Vli, and means tor maintaining supervision ot said connection over said third trunk.

16. ln a telephone system, a irst group oft lines, a branch 'tor each line ot said group, a second group of lines, a `oranch Jfor each line of said second group, means tor extending a connection trom anj.7 line ot said irst O'roup to any line ot said second group via Aheir respective branches, means for by- )assing the branches ot said lines, and mel 'is tor maintaining supervision ot the connection over the branch ot the line ot the second group. l

l?. ln a telephone system, aV irst and a sec ond line, means tor connecting said lines, a link circuit having termina-ls at each end, automatic switching' mechanism means ter operating said mechanism to connect one end ot said link circuit to said second line and the other end ot said link circuit to said tirst line, and means for maintaining said mechanism operated over said second line independent ot said operating means. p

18. ln a telephone system, a iirst and a sccond line, a link circuit having terminals at each end, automatic switching mechanism, operator-controlled means tor operating said mechanism to connect one end ot said link circuit to said second line andthe other end of said link circuit to said tirst line, and means for maintaining said mechanism operated over said second line independent of said operating means.

19. Ina telephone system, a first line, a

`second line, 'a subscriber's line, anautomatic switch terminating ysaid second line, a cord circuit, operator-controlled.means for establishing a connection from said first'line to said subscribers line via said cord circ-uit, said second line, and said automatic switch, a link circuit, vand f operator-controlled means for connecting said first line to said automatic switch directly via said link circuit independent of said cord circuit and said second line.

20. In a telephone system, a first and a second line, a subscribers line, an automatic switch terminating said second line, operator-controlled means for establishing a connection from said first line to said subscribers line via said second line and said automatic switch, a link circuit, and operatorcontrolled means for connecting said rst line to said switch directly via said link circuit independent of said second line.

2l. In a telephone system, a first and a second line, a` subscribers line, an automatic switch terminating said second line, operator-controlled means for establishing a connection from said first line to said subscribers line via said second line and said automatic switch, a link circuit, operator-controlled means for connecting said first line to said switch directly via said link circuit independent of said second line, and means for maintaining the latter connection int-act independent of the latter operator-controlled means.

22. In a telephone system, a first and a second line, a subscribers line, an automatic switch terminating said second line, operator-controlled means for establishing a con-- nection from said first line to said subscribers line via said second line and said automatic switch, a link circuit, operatorcontrolled means for connecting said first line to said switch directly via said link circuit independent of said second line, and means for maintaining the latter connection intact over said second line.

23. In a. telephone system, an automatic exchange, a toll board, a trunk line passing through said exchangeand extending to said toll board, operator-controlled means for establishing a connection from said trunk line to a subscribers station at the automatic exchange, and auxiliary apparatus at the automatic exchange for establishing a connection from said trunk line to said subscribers station exclusive of the section of the trunk line extending from the automatic exchange to the toll board.

24. In a telephone system, an automatic exchange, a toll board, a toll line passing through said exchange and extending to said toll board, a service trunk extending from said toll board to said automatic exchange, means including said service trunk for establishing a connection from said toll line to aV station exclusive of the section of the toll 70 line betweengthe automatic exchange andthe Atoll board and .also exclusive of said service trunk.

25. In a telephone system, an automatic exchange, a toll board, a group of toll lines passing through said exchange and extending tosaid toll board, a group of service trunks extending from said toll board to said automatic exchange, means for extending connections from the'toll lines via the service trunks to subscribers stations at the automatic exchange, a plurality of switching mechanisms at the automatic exchange, and a common control circuit for operating said switching mechanisms separately to by-pass the sections of the toll lines between the automatic exchange and the toll board and also the service trunks included in such connections.

26. In a telephone system, an automatic exchange, a toll board, a group of toll lines passing through said exchange and extending to said toll board, a group of service trunks extending from said toll board to said automatic exchange, means for extending connections from the toll lines via the service trunks to subscribers stations at the automatic exchange, aplurality of switching mechanisms at the automatic exchange, and means for maintaining each switching mechanism operated independent of the common control circuit over the service trunk by-passed thereby.

27. In a telephone system, a first and a second line, a plurality of link circuits having terminals at each end, a selecting switch for selecting an idle one of said linkcircuits, operator-controlled means for connecting the terminals of one end of the selected link circuit to said first line and the terminals of the other end of the selected link circuit to said second line to connect said lines, and means for causing said selecting switch to select the next idle link circuit at the completion of said connection.

28. In a. telephone system, a first and a second line, a plurality of switching mechanisms, a selecting switch for selecting an idle switching mechanism, a third line terminating in said selecting switch, means controlled over said third line for operating the selected switching mechanism to connect said first and said second line, and means responsive to the completion of said connection for causing said selecting switch to Select another idle switching mechanism.

29. In a telephone system, a first and a. second line, a plurality of switching mecha.- nisms, a selecting switch for selecting an idle switching mechanism, a third line terminating` in said selectingI switch, and means ated switching mechanism in position until controlled over said third line for operating the termination of the call. the selected switching mechanism to connect In Witness whereof, I hereunto subscribe l0 said first and said second line to extend a my name this 20thv dayv oi February A. D.,

5 call, means for then causing said selecting 1926.

switch to select another idle switching mech- A anism, and means for maintaining the oper- Y BERNARD D. WILLIS. 

